Deprecation warning during sbt clean assembly

[Gerrrr]

$ sbt clean assembly
[info] Loading project definition from /Users/gerrrr/Work/ddq/project
[info] Updating {file:/Users/gerrrr/Work/ddq/project/}ddq-build...
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
/Users/gerrrr/Work/ddq/build.sbt:39: warning: `<<=` operator is deprecated. Use `key := { x.value }` or `key ~= (old => { newValue })`.
See http://www.scala-sbt.org/0.13/docs/Migrating-from-sbt-012x.html
pythonItAssembly <<= assembly map { (asm) => s"cp ${asm.getAbsolutePath()} python/drunken-data-quality.jar" ! }